As will be appreciated by those skilled in the art, specialized helical shaped devices such as screw conveyors are well known for the transport of various bulk material. Such conveyors generally include a helical shaped member which rotates within a housing or trough such that rotation of the screw conveyor along its longitudinal or central axis results in movement of the bulk material along the length of the device. In the past, such conveyors were typically constructed from metal and each conveyor was specifically designed for a particular purpose and of a particular length. However, although most prior art conveyors were specifically designed to meet a particular application, there had been some attempts of providing a modular type conveyor of metal and/or wood. Examples of U.S. Patents which disclose such modular conveyors include U.S. Pat. No. 349,233 issued to James Nelson on Sept. 10, 1886; U.S. Pat. No. 455,384 issued to H. Birkholz on July 7, 1891; U.S. Pat. No. 525,194 issued to J. Dyson, et al on Aug. 20, 1894; U.S. Pat. No. 546,879 issued to J. Dyson, et al on Sept. 14, 1895; U.S. Pat. No. 1,867,573 issued to D. G. Leach on July 19, 1932; U.S. Pat. No. 2,492,915 issued to A. B. Carlson on Dec. 27, 1949; U.S. Pat. No. 3,648,826 issued to Dean P. Brooks on Mar. 14, 1972 and U.S. Pat. No. 3,705,644 issued to Claude E. Kawchitch on Dec. 12, 1972. However, a study of the above patents indicates that only the two Dyson, et al patents, the Nelson patent and the Kawchitch patent can be considered sectional or modular. In addition, the assignee of the present application filed an application for Letters Patent on Sept. 29, 1983 for a "Modular Screw Conveyor" and which has Ser. No. 537,345, abandoned, and on Apr. 4, 1984 filed an application for "Mold and Process for Manufacturing Helical Shaped Items" which has Ser. No. 598,374, U.S. Pat. No. 4,693,861. An application entitled "Concealed Drive Coupling for Use With Modular Screw Conveyor" and having Ser. No. 822,641, U.S. Pat. No. 4,691,818, was filed on Jan. 27, 1986. This application is also assigned to the assignee of the present invention.
In addition, it is believed that apparatus is available for bonding sections of plastic pipes together in a fluid or liquid tight manner by heating the ends and pressing the melted ends together. However, the techniques and the overall concept as applied to bonding the edge of flights of adjacent modular screw conveyor sections together is believed to be unique and different from that of bonding plastic pipe together.
As will be appreciated, one of the advantages of the plastic modular screw conveyor is ease of cleaning due to the smooth and non-interrupted surfaces. Also of course, by axially stacking any selected number of modules on the non-circular drive shaft a screw conveyor of any length can be fabricated. For certain applications, it is desirable the confronting edges of the flights of adjacent modules be sealed to each other to strengthen the conveyor and to eliminate any large spaces between the flights which might trap particles of the conveyed material. However, to pass the USDA requirements any process which fills up spaces between flights must not result in any small cavities or openings which could harbor bacteria.
Therefore, it is an object of the present invention to provide apparatus and methods for joining or bonding the confronting edge of a flight of one module to the confronting edge of a flight of a second module in a crevice-free manner.
It is another object of the present invention to provide apparatus and methods which results in a bond or joint such that the joined flight members are in register with each other.
It is yet another object to provide apparatus and methods which allows the flights of a multiplicity of modules to be joined together.